An even simpler formula is use the DOF preview on the camera and look through the viewfinder. When in doubt, stop down a stop or two. My desire is to make pictures, not get involved with mathematics.
Bill ----- Original Message ----- From: "graywolf" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Friday, April 09, 2004 2:50 PM Subject: Re: Zone Focus - what is it? > A much simpler formula is: H = 1000 * D, where > H is Hyperfocal-distance, and > D is diameter-of-the-aperture. > (1000 * D assumes an 8x10, or 8x12 print regardless of the format.) > > You can determine D from: D = f / N, where > f is focal-length, and > N is f-stop. > (Note: f and N are used only to determine the aperture. They have no direct > affect on DOF or H.) > > DOF can be determined from: > Dn = H * Ds / H + Ds, and > Df = H * Ds / H - Ds, Where > Ds is subject-distance (or focus-point), > Dn is near-distance, > Df is far-distance. > > Advanced cameras usually have a DOF scale based upon an 8x10 print, thus these > formulas have direct application. Many snapshot cameras used 5x7 since they are > less likely to have large prints made. You can simply change the f-stop opening > up one stop for 5x7 and two stops for 4x6 prints. Normally you do not have to > close down for larger images because they are intended to be viewed from farther > away. > > ZONE FOCUS is nothing more than setting the camera so that the anticipated > action is within the DOF range. In other words some place between Dn & Df. Then > to take the photo you do not have to adjust the focus when shooting. > > As others have mentioned you can simply use the DOF scales on your lens, if it > has them, some zooms do not. Otherwise a table generated from the above tables > will work very well. > > -- > > Jens Bladt wrote: > > > Hyperfocal distance (H) is a way to dertemine the distance to focus the lens > > for a given aperture and focal length to ensure maksimum DOF, when you want > > sharpness to infinity (e.i. landscape photograph): > > > > H = FxF/fc > > F being Focal length > > f being f-number (aperture) > > c being the diameter of Circle of Confusion (CoC could be 0.021mm for 35mm > > negs enlarged to a 8x10 print). > > > > At 70mm lens f8 "H" would be (35mm neg): > > 70x70/8x0.021 = 29167 mm = 29.2 meter > > > > This means, that if you set the distance to 29.2m, > > you will get sharpness (on a 8x10 inch print) from infinity to as close as > > you can get at f 1:8 > > > > If you are a landcape photographer, you should have a table in your camera > > bag giving "H" for the most used focal lengths at let's say f22 or 32. > > > > At f22 the math should be: "H" = 70x70/22x0.021mm = 10.6 meter > > The near limit of sharp focus is: > > > > Fu(F+cf)/FxF+ufc > > (u being the used distance in mm) > > > > 70X10606(70+22x0.021)/70x70+10606x70x0.021)= 5338mm = 5.3m. > > The image (8x10) will appear sharp from 5.3m to infinity at f22 when focus > > distance is set to 10.6m > > Source: Andrew Hawkins & Dennis Avon; "Photography", UK 1979. > > > > all the best > > > > Jens Bladt > > > > mailto:[EMAIL PROTECTED] > > http://hjem.get2net.dk/bladt > > > > > > -----Oprindelig meddelelse----- > > Fra: Doug Franklin [mailto:[EMAIL PROTECTED] > > Sendt: 9. april 2004 06:33 > > Til: [EMAIL PROTECTED] > > Emne: Re: Zone Focus - what is it? > > > > > > On Fri, 9 Apr 2004 07:25:27 +0200, Boris Liberman wrote: > > > > > >>Please enlighten the ignorant, as usual... > > > > > > Using the hyperfocal distance of the lens, possibly modified, to make > > sure that everything you're likely to shoot is in focus. For example, > > take your lens and figure out what f-stop you want to use. The turn > > the focus ring until the infinity mark lines up with the "tic mark" for > > the f-stop you're using. The "tic mark" on the other side of center > > will tell you what's going to be in focus. So, just to pull some > > numbers out of thin air, you pick f/5.6. When you line up the infinity > > mark on the focus ring with the "5.6" tic on the barrel you might find > > that the opposite tic indicates 10m. That means everything from 10m to > > infinity will be in focus. So you don't worry about focusing unless > > the target is closer than 10m. You can shift it closer if you're not > > worried about things at "infinity" distance. > > > > TTYL, DougF KG4LMZ > > > > > > > > > > > > -- > graywolf > http://graywolfphoto.com/graywolf.html > > > >
